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What is Coenzyme Q10 (CoQ10)? + Side Effects & Dosage

Written by Aleksa Ristic, MS (Pharmacy) | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Aleksa Ristic, MS (Pharmacy) | Last updated:

CoQ10 is a popular supplement used to boost energy levels, protect the heart, and reduce the side effects of statins. It is important for proper mitochondrial function, heart health, muscle function, and more. Read on to learn the how it works & the possible side effects.

What is Coenzyme Q10?

Coenzyme Q10 (CoQ10) is an important compound found in every cell in the body. It is a type of coenzyme, which means that it helps enzymes work more effectively. CoQ10 is mainly located in the membrane of mitochondria, where it is used to make energy [1].

CoQ10 helps shuttle electrons in the mitochondria to produce ATP, the main form of cellular energy [2].

It is also found in cell membranes and in lipoproteins – such as LDL and HDL – where it acts as a powerful antioxidant. CoQ10 stabilizes cell membranes, helping cells work properly [3].

Energy-demanding organs in your body have the highest levels of CoQ10. These include the brain, heart, kidneys, muscle, and liver – all of which contain many mitochondria and use a lot of energy [1].

Many different diseases and conditions, as well as nutrient deficiencies, can reduce the body’s ability to make CoQ10 or cause CoQ10 to be used up faster than it can be replaced. In these cases, supplementation may be helpful or necessary [4].

CoQ10 is commonly supplemented to help improve diseases that involve mitochondrial dysfunction and increased oxidative stress such as fibromyalgia, chronic fatigue syndrome, and diabetes. Supplementation may also be beneficial for heart diseases, including heart failure [4].

Some people also take CoQ10 supplements to combat the side effects of statins. Athletes, on the other hand, use them to enhance performance [5].

For more about the potential benefits of supplementation, check out this post.

Coenzyme Q10 (CoQ10) is a vital compound that helps the mitochondria produce energy. Some people with nutrient deficiencies or diseases and those taking certain medications may need to supplement, while athletes use CoQ10 supplements to improve performance.

Food Sources

The body makes about half of the CoQ10 we need, while we get the rest from food. Excellent sources of CoQ10 include [4, 6, 7]:

  • Meat: beef, chicken, and pork (highest levels in the heart and liver)
  • Fish (herring and sardines, highest levels in the heart)
  • Seafood (shrimp and scallops)

Foods containing much lower CoQ10 levels include [6, 7]:

  • Dairy
  • Eggs
  • Nuts (highest in sesame seeds)
  • Legumes (highest in peanuts)
  • Vegetables (highest in parsley and soybeans)

Ubiquinone vs. Ubiquinol

CoQ10 is mainly found in two forms in the body: ubiquinone and ubiquinol. Ubiquinone is the oxidized version in the body that is recycled (reduced) back into ubiquinol and vice versa. Ubiquinol is primarily responsible for the antioxidant benefits of CoQ10, although ubiquinone may have some antioxidant potential [8, 9].

Ubiquinol makes about 90% – 98% of the CoQ10 in the blood, while ubiquinone makes only a small percentage. Both forms are carried around the body by LDL and HDL. The ratio of ubiquinol to ubiquinone decreases as you age due to poor conversion between the two forms and increased oxidative stress [10, 11, 12, 13].

Ubiquinol and ubiquinone are different forms of CoQ10. Ubiquinol is the active form.

Antioxidant Effects

CoQ10, in its ubiquinol form, is a strong antioxidant that protects the cell and mitochondrial membranes. But even in its oxidized form as ubiquinone, it may still have some antioxidant effect [1, 9].

The membrane that surrounds cells contains fats that help keep it stable. These fats can become oxidized and damaged, which causes the cell to not work as well. CoQ10 is found within the cell membrane where it acts to prevent this oxidative damage [14].

CoQ10 is carried around the bloodstream by lipoproteins such as LDL and HDL. LDL is especially prone to becoming oxidized, when it becomes more dangerous than regular LDL and may trigger plaque formation and hardening of the arteries. CoQ10 helps prevent LDL from becoming oxidized [15, 16, 3].

As ubiquinol, CoQ10 protects blood lipids and cell membranes against oxidative damage.

Coenzyme Q10 Safety & Precautions

Side Effects

This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.

CoQ10 is generally very well-tolerated, even at the high doses. Side effects are mild and include [17]:

  • Upset stomach
  • Diarrhea
  • Nausea
  • Loss of appetite
  • Headache
  • Rash

CoQ10 is processed by the liver and is eliminated through bile. This means people with poor liver function or blocked bile ducts who supplement with CoQ10 may accumulate high levels in their body, increasing the risk of side effects [17].

CoQ10 is considered very safe, though some people may experience digestive side effects, headache, or rash.

Drug Interactions

Supplement-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let them know about all drugs and supplements you are using or considering.

Warfarin (Coumadin)

CoQ10 is structurally similar to vitamin K, which has blood-clotting effects and can interfere with the effectiveness of warfarin [1, 18].

There have been multiple case reports of CoQ10 reducing the effectiveness of warfarin [19, 20, 21].

Blood Pressure-Lowering Drugs

CoQ10 can reduce blood pressure. The combination with blood pressure-lowering drugs may lead to very low blood pressure [22, 23, 24, 25].

Blood Sugar-Lowering Drugs

CoQ10 can reduce blood sugar levels. The combination with blood sugar-lowering drugs may further lower blood sugar [26, 27].

Theophylline (Elixophylline, Theochron)

CoQ10 increased the time it took the drug theophylline (used to treat asthma and COPD) to reach peak blood levels in rats. People taking theophylline should consult their doctor before supplementing with CoQ10 [28].

CoQ10 may interact dangerously with certain medications. To avoid unexpected interactions, talk to your doctor before supplementing.

Coenzyme Q10 Dosage & Supplement Forms


The below doses may not apply to you personally. If your doctor suggests using CoQ10, work with them to find the optimal dosage according to your health condition and other factors.

CoQ10 supplements come in two forms: ubiquinone and ubiquinol. If the supplement label only has “CoQ10” on it, then it is most likely ubiquinone.

For most of the studied diseases and conditions, 100 – 300 mg of ubiquinone divided into two daily doses is effective. Higher doses may be needed to see improvement in neurodegenerative diseases [29, 14, 30, 31, 24, 32, 33, 34].

Taking a dosage of 1,200 mg of ubiquinone daily is safe long-term. Up to 3,000 mg daily may be safe in the short-term (up to 2 weeks). However, doses above 2,400 mg/day do not result in any further increase in blood CoQ10 levels [34, 33, 35, 36].


CoQ10 is fat-soluble, meaning it is best absorbed when taken with a meal that contains oils or fats. CoQ10 formulations that are mixed with oil are absorbed better than powders and pills. Taking vitamin C and vitamin E at the same time as CoQ10 may reduce its absorption [1, 37, 38].

Even when it is consumed with a fatty meal, CoQ10 is still poorly absorbed. Absorption also varies greatly between people due to differences in gut bacteria and the ability to absorb fats [39, 38].

CoQ10 is often combined with vitamin E to enhance its antioxidant effects [1].

User Reviews

The opinions expressed in this section are solely from the users who may or may not have a medical background. SelfDecode does not endorse any specific product, service, or treatment. Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice because of something you have read on SelfDecode.

People who supplement with CoQ10 generally report increased mental and physical energy levels as well as improved strength and stamina. Fibromyalgia patients report decreased pain in addition to improved energy and mental clarity. Some users do report fatigue and brain fog when taking it.

Buy CoQ10

Further Reading


CoQ10 is vitally important to maintaining energy levels and preventing oxidative stress throughout the body, especially in the heart. Low levels of CoQ10 can be caused by various diseases, conditions, nutrient deficiencies, and statin drugs.

CoQ10 is safe and only has mild side effects, but it can reduce the effectiveness of blood-thinners. Absorption of CoQ10 is poor, so it should be supplemented with a high-fat meal. Up to 1,200 mg/day is safe for long-term supplementation.

About the Author

Aleksa Ristic

Aleksa Ristic

MS (Pharmacy)
Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets.  
Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.


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